The present invention relates generally to a wire cutting type electrical discharge machining system for machining an electrically conductive workpiece by means of an electrical discharge energy which is generated between a continuously fed wire electrode and the workpiece. More particularly, this invention relates to a movable flexible tube for easy insertion of the wire electrode into a wire passage.
In a traditional electrical discharge machining system, an electrode in the form of a wire is guided by wire guides along a predetermined path which is formed outside the machine frame. For better appearance of the machine and improved safety, a wire passage defining the wire path except its portion in the vicinity of the workpiece is preferably formed within the machine frame. In this case, it is difficult and troublesome to thread or insert the wire electrode through or into the wire passage. For example, a lower wire passage is formed within a lower arm which extends laterally from the column of the machine. The lower arm carries at its outer free end a lower wire guide which cooperates with an upper wire guide to guide the wire electrode so that the wire electrode runs across the workpiece positioned between the upper and lower guides. Therefore, the free end of the lower arm and consequently the lower wire guide are located below the workpiece. In this arrangement, it is a very hard job to insert the wire electrode into the wire passage through its outer end located below the lower wire guide which is located below the workpiece. Such insertion of the wire electrode is required when the wire electrode is initially threaded through the machinig system, or when it is cut off during a machining operation. This difficulty in inserting the wire electrode stems from the geometrical arrangement wherein the workpiece and the lower wire guide prevent an easy access to the inlet of the wire passage.